The following disclosure relates generally to communications systems and, more particularly, to controlling overload in a telecommunications system.
Telecommunications systems are generally designed to operate at or below a certain traffic capacity. This means that they can successfully service traffic up to that capacity, but the service starts to deteriorate when the capacity is exceeded. When this occurs, the system goes into “overload” and, in some situations, may fail entirely.
One or more overload control measures may be implemented in such telecommunication systems in an attempt to regulate or at least minimize the impact of traffic overload. These control measures generally operate by “throttling” the traffic (e.g., permitting only a portion of the traffic to pass through the system). For example, a percent blocking throttle approach blocks and rejects arriving traffic with a given probability. A call gapping throttle rejects traffic for a certain predefined period of time and then accepts traffic for another predefined period of time (e.g., traffic is allowed through the “gap” that exists when the throttle is open). A token bank throttle uses “tokens” to regulate the traffic by allowing only the traffic with a token to pass through the throttle.
However, none of these control measures adequately address the complexities presented by traffic patterns in telecommunications systems. For example, none of the above control measures is suitable for handling “mixed” traffic that includes multiple types of messages. Likewise, none of the above control measures is suitable for differentiating between classes of service. Traffic is rejected regardless of its class. Furthermore, some of the measures fail because they are unable to compensate for varying overload onset rates. For example, if an overload occurs more rapidly than the control system was designed to handle, the system may fail to control the overload. A further problem is that the previously described control measures are generally designed for a specific overload condition having specific traffic parameters and so are unable to react appropriately when an overload occurs that does not fit within the system's parameters.
Accordingly, what is needed is a system and method for controlling overload that is capable of handling a variety of message types, message classes, and overload onset rates while also being adaptable to handle non-specified overload events.